An air filter in an MX5 NB (1998 - 2000) is the first line of defense between outside air and engine interior. The filter blocks dirt particles while allowing air to flow as freely as possible toward the intake and combustion chamber. As a filter gets dirty, resistance builds up in the airflow and you often notice that response and breathing of the block feel a little less free. When the intake side of intake and sensors also remain clean and functioning properly, the engine benefits immediately.
